Municipal alarm service



(No Model.) 2 Sheets-Sheet 1.

W. A. STERN. 4 MUNICIPAL ALARM SERVIGE. No. 333,975. Patented Jan. 5, 1886.

G'ro laid,

n. PETERS FhvlmLilhvgrapher Washinglon, o. c.

(No Model.)

' 2 SheetsSheet 2. W. A. STERN. Q

MUNICIPAL ALARM SERVICE.

Patenti-ni Jan. 5, 1886-.

Inventor VVitnesse y 1 VGlWMMr N. PETERS, Plvolo-Uthagrapher. Waihingwn. 0. c.

Nrrnn STATES ATENT WILLIAM A. STERN, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR OF ONE- HALF TO EUGENE INGOLD, OF SAME PLACE.

MUNICIPAL ALARM SERVICE.

SPECIFICATION forming part of Letters Patent No. 333,975, dated January 5, 1886 Application filed January 5, 1885. Serial No. 151,981. (No model.)

To all whom it may concern.-

Be it known that I, WILLIAM A. STERN, of Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Municipal Alarm Service; and I do hereby declare the following to be a full, clear, and exact description thereof.

My invention relates to an electric call or signal system for fire-alarm, police, and other like service, in which a central station and a number of signal or call stations are used.

Its special characteristic consists in the use of one wire for transmitting several and distinct signalsby means ofseparate instruments which are so differentiated that when one instrument is being used all of the others are inert, and so that no instrument is capable of transmitting m re than its special signal.

The object of my invention is to cheapen and simplify the construction and operation of such systems, to obviate the danger of mistakes, and to dispense as far as can be with the intervention or the necessity for the exercise of human intelligence by making the en- ]tOire apparatus as nearly automatic as possi- I am aware that there are other existing systems in which several different signals are sent by a single instrument from a station to the central office by moving a lever in the transmitting-instrument certain fixed distances, so as to allow the circuit-breaking wheel to turn far enough to give the required signal; but in this apparatus there is a constant liability of mistake, for such signals are usually given by a person laboring under more or less excitement, and if the lever is not moved exactly the required distance the wrong signal will be transmitted. Practical experience has shown this to be a fruitful cause of trouble, and in a system of police regulation, which depends on certainty in this regard for its efficiency and success, mistakes of this kind are constantly liable to result in loss of life and property. In fact,

mistakes very often occur in the now common system of fire-alarm telegraphy simply because the lever is not moved the correct distance. They are much more liable to occur in the more complex systems,upon which my invention is an improvement.

Another objection to the systems which use a common receiving-instrun'lent for several different signals is the delay in translating and 5 separating-them. If the signal involves the sending out of an ambulance or of the fireservice, the central operator after receiving the signal must repeat it on another instrument to the proper station. Here, in addition to the delay, is further liability for mistake, especially when several messages are received at the central station at or about the same time from several different signal-stations. If the ambulance or fire-engine horses are to be released by appropriate instruments actuated by the signal-current, the intervention of the central office is necessary, because otherwise the horses would also be released by other signals when they are not needed. This would tend to destroy their efficiency.

In my improved system everything except the mere matter of moving the lever of the appropriate signal or transmitting instrument is automatic. I have a separate instrument for sending each signal, which instrument can send no other signal; a separate instrument for receiving the signal, which can receive no other signal, and a single wire for transmitting all the signals, the various transmitting and receiving instruments being all connected to said single wire, but so difi'erentia'ted that all remain inert,-except the one which is being used to send the signal and its correspondinglyadjusted receiver. The receiving-instrument records the signal at the central office, and at the same time transmits it automatically to the proper stations, where it is recorded, and the horses, if any, liberated.

To enable others skilled in the art to make go and use my invention, I will now describe it by reference to the accompanying drawings, in which- Figure 1 is a diagram illustrating the arrangement and operation of the apparatus by 5 which my improved system is carried out in practice, said diagram being limited to one transmitting or signal station and one receiving-station. the system as applied to a central and several signal stations. Fig. 3 is a detail.

Like letters of reference indicate like parts in each.

Referring now to the receiving-instruments, a, a, a and a are difierential electro-magnetsthat is, magnets having the cores surrounded by two windings of insulated wire, so that if currents of equal strength are passing in opposite directions over the wires the effect of one current upon the core of the magnet would be entirely neutralized by the effect of the other. These instruments are placed in a receiving or central station, A. The magnet a has a core, I), and an armature, a, mounted upon an armature-lever, cl, which is provided with a retractile spring, 6. The lever d vibrates between the core I) and a contact-point, f, placed on the opposite side. The magneta is connected with the battery {1 by means of a wire, 1, which, before reachingthe magnet, is divided into two branches, 2 3, both of which are coiled around the core bin such a manner that the current from the wire 1, which passes over one of them, shall pass in the opposite direction over the other. One of these wires is connected to a wire, 4, which returns to the battery 9, and the other is connected to a wire, 5, which extends to a wire, 6, said wire 6 be ing in turn connected with the line-wire 7, which leads to the signal-station.

Preferably arranged in the wire 4 is an adjustable resistance device, h, and thence the wire 4 connects by the wire 11 with the groundwire 9 of the battery 9 or directly with the ground. The other three magnets, a a. a have similar parts and wire connections, and each is arranged and connected in the same manner as the magnet a, just described, through a separate resistance, h h h with the groundwire 9.

In the receiving-station A is a second battery, 1', one pole of which is connected by a wire, 8, with the base-plate of each armaturelever d d d' (P, and the other pole by a wire, 9, with registering-instruments k kk' and with sounders Z Z Z and watchmans clock m, all of which in turn are connected by wires with the contact-pointsfff f I will now describe the apparatus of the signal-station B and its arrangement. Here I provide circuit-breaking wheels n, of the usual construction, said wheels being provided with projecting teeth, which, when the wheels are rotated, come in contact in passing with contactsprings 1). Each wheel is electrically connected by a conductor, 0, with an adjustable resistance, 12, in this instance composed of a stick of carbon, q, capable of being immersed more or less in a cup of mercury, 7, each of said cups being grounded, as at s.

The diagram just described is designed to illustrate the construction and operation of my improved system provided with four separate callssay, forinstance, police, fire, ambu- Fig. 2 is a diagram illustratinglance, and police time reports. There is an instrument in each signal-station which is designed to send each one of these signals, and a corresponding instrument in the central office for receiving such report. The resistance of each of these corresponding transmitting and receiving instruments is the same; but it differs from the resistance of the-other three couples shown in thediagram, and served by the same common line-wire 7. The magnets a, a, a and a are each so wound as to measure a different resistance, or they are included in a circuit of different resistance from that of the others, and the wheels or n n n are arranged in multiple are so that only the particular wheel which is sending the signal is in circuit at the time such signal is sent. \Vhile the circuit is open at the signal-station B, which is its normal condition when no signal is being sent, the current from the battery 9 passes over all of the magnets, but only by the wires 2 and 4, and in one direction, so that the cores of the magnets are sufficient y magnetized to overcome the tension of the springs e and attract the armatures 0, thereby breaking the contact between the levers d and the points f. When a signal is given at thestation B-say by means of the wheel nthe closing of the external circuit, which includes n, permits a current to pass over the wires 3, 5, and 7, which current, being of equal strength with and passingin the opposite direction from that passing over the wires 2 and 4, neutralizes the magnetic effect of the latter upon the core b, thereby releasing the armature c and permitting the spring 6 to retract it from the core I) and bring its lever d in contact with the point f. The instant the armature-lever (1 comes in contact with the point f the circuit from battery 1' through the register In and bell-magnetl is closed, and the signal which is sent from the station B by means ofthe wheel a is recorded in the central station,A. This operation has no effect upon the magnets a, a", and a and their circuits for the reason that the resistance in the circuits of those magnets is not the same as that of the circuit in which the wheel a is located. By including in the circuit of the battery z, which is closed by the retraction of the lever d, the necessary instruments and connections the signal that is given will be repeated in the fire-service station 0, Fig. 2, p

where, by use of known apparatus, not necessary here to describe, the horses may be liberated at the same instant by the current which transmits the signal. The same description applies exactly to the transmission of a signal from any of the other signal-wheels n n a Whenever a signal is given by means of any one of these wheels, a circuit having a resistance equal to the circuit which includes the corresponding relay in the central station is closed with the latter. The second current passes in the opposite direction from the first and neutralizes the magnetic effect of the first current on the core of the relay, so that the armature of the same is retracted by its spring, and thereby the circuit of the recording-instrument connected with the relay is closed, so as to record the signal. At the same time, as before stated, the resistance of the other relays or magnets being different from that of the relay which is thus brought into circuit, the cores of such other relays are not demagnetized and consequently hold their armatures in contact with them. As the transmitting-instruments in the station B are fitted to transmit only a single signal, there is no necessity of any. mistake being made on the part of the sender of the signal if the boxes containing said transmitting instruments are plainly marked with the name of the service for which they are designed. Toinsure against such a partial movement of the lever 11, Fig. 3, of the transmitter 17. as will not set the wheel of the transmitter in motion, I have provided the lever with a bell, t, so arranged that when it is properly moved to start the wheel the bell will be sounded. The resistance devices h h h h are placed in wires 4 for the purpose of adjusting the resistance of each internal circuit so as to be exactly equal to the corresponding external circuit, which is also provided with an adjustable resistance, (1. In this way the utmost exactness can be secured.

It is apparent that by simply increasing the number ofdifierential relays or magnets and by making them of different resistances the nu mber ofsignal-stations which can be operated by my system from a single central station can be multiplied indefinitely. Itis also apparent that-the danger of mistake is reduced to a miniinum,as the entire apparatusis automatic with the exception of the moving of the lever by which the transmitting-instrument is released.

I propose to make the station-boxes B of sufficient size to accommodate, in addition to the instruments, a chemical fire-extinguisher of suflicient size to answer for simple emergencies, and thereby to render the plant more perfect and efficient for general municipal purposes.

Asanother provision for insuring certainty, I have provided an electric hell, it, in the conductor 7, at the station 13, which bell will be sounded when the circuit is closed to the receiving'instrument,rand will indicate to the sender of the call the fact of its reception at the central station. If the bell u shouldnot sound,it is evidence to the sender that the circuit has not been closed and no signal has been transmitted. Thus defects in the apparatus will be much more liable to early detection.

If desired, fixed resistances may be substituted for the adjustable resistances g. In determining the measure of such aresistance the resistance of the entire circuit composed of the conductors 3, 5,6, 7, and O, and of the instrument a must be determined, and the difference between the same and the resistance of the circuit of the relay a will be the measare of the permanent resistance device which is substituted for q. The resistance of the lineconductor increases with its length, its diameter and material remaining the same, and as the transmitting-instruments are nearly all placed at different distances from the central office the measure of the permanent resistances thus used would differ accordingly, so that special resistance devices would need to be made for each signal-station, which would cause great trouble and expense. On the other hand, the adj ustable resistance devices (1 can. all be made of the same pattern, and after being set up be adjusted to the proper register without trouble.- I preferto use the mercurycup and carbon, because this form is not affected by temperature, evaporation, and other deteriorating causes. a

\Vhen I speak of the resistance of the relay, I mean the resistance of its entire circuit and included devices; and when of the resstance of the branch circuit, I mean the resistance of the line, the branch and itsincluded devices. By the use of the adjustable resistance device h in the relay-circuit I am enabled to make all the relay-instruments of one pattern, thereby saving expense and trouble, and then when they are set up give each relay-circuit a different resistance by simply adjusting the device h.

XVhile I have described my invention as applied to use in a signal service, I do not limit myselfthereto so far as the combination of several differential relays having different resistances, a common line conductor, and several branch conductors, each having a resistance equal to that of one of the relays, is concerned, as it is applicable to other uses.

Differential galvanometers having local contact-points may be substituted for the relays, the deflection of the needle being utilized in place of the movement of the armature; or, electro-magnets having permanently magnetized cores with one winding of insulated wire may be substituted for the relays. In such case the current is used to demagnetize the core temporarily, thus securing the differential effect. These devices are the equivalents of the relays, and as such I include them in my claims under the term differential relays. I prefer, however, the construction first described for obvious reasons.

I am aware ofthe Patent No. 245,272, granted to Bright on August 9, 1881, and hereby disclaim the same.

What I claim as my invention, and desire to secure by Letters Patent, is

1. The combination of several differential relays, each in a branch of the main circuit, having a different resistance from the others, with a common line-conductor, and several branch conductors, each leading from the lineconductor and having a different resistance from the others, which corresponds to that of one of the relay or branch circuits of the main line.

2. The combination of several differential relays, each being arranged in a main circuit and having a different resistance from the others, a common line conductor, several branch conductors, each leading from thelineconductor, a signal-instrument included in each branch conductor, and a resistance device, also included in each branch conductor, which shall equalize the resistance of such branch circuit with that of the main circuit of one of the relays, substantially as and for the purposes described.

3. The combination of several differential relays, one coil of which is connected with the opposite poles of the battery of the main line which furnishes a circuit for each relay, adjustable resistance devices arranged in each such relay-circuit, a line-conductor connected with the other coil of the relays, and several branch conductors leading from the line-condnctor, each containing an adjustable resistance device, substantially as and for the purposes described.

4. The combination, in several branch circuits, each having a difl'erent resistance, of several differential relays, one coil of each relay being connected with the opposite poles of the battery of the main circuit, and the other coil with aline-conductor, and several branch conductors leading from the line-conductor, each containing a resistance device, substantially as and for the purposes described.

5. The combination of several differential relays of different resistances, a common lineconductor to which one of the coils of each relay is connected, several branch conductors leading from the line-conductor, each branch containing a signal-transmitter and having a resistance equal to that of one of the relays, a local circuit connecting with each relay, which circuit is closed by the armature-lever of the relay when retracted, and signal-instruments arranged in such local circuit, substantially as and for the purposes described.

In testimony whereof I have hereunto set my hand this 2d day of January, A. D. 1855.

\VILLIAM A. STERN.

Vitnesses:

THOMAS E. KERR, W. B. GORWIN. 

